This is true - in general, a warning means the code is non-standard or ambiguous, so the compiler is falling back to some default or non-standard interpretation

This is true - in general, a warning means the code is non-standard or ambiguous, so the compiler is falling back to some default or non-standard interpretation. Then, people come to rely on that, and, like you say, not turn warnings on. So, I say that's not a useful class of behavior, and in some cases (trying to write secure / portable software) it would be better if that didn't exist.